/**
 * Minimal Discord Gateway connection to keep the moderator bot "online".
 * Uses Node.js built-in WebSocket (Node 22+).
 */

let ws: WebSocket | null = null;
let heartbeatInterval: ReturnType<typeof setInterval> | null = null;
let lastSequence: number | null = null;
let sessionId: string | null = null;
let resumeUrl: string | null = null;
let reconnectTimer: ReturnType<typeof setTimeout> | null = null;
let destroyed = false;

type Logger = {
  info: (msg: string) => void;
  warn: (msg: string) => void;
};

const GATEWAY_URL = "wss://gateway.discord.gg/?v=10&encoding=json";

function sendPayload(data: Record<string, unknown>) {
  if (ws?.readyState === WebSocket.OPEN) {
    ws.send(JSON.stringify(data));
  }
}

function startHeartbeat(intervalMs: number) {
  stopHeartbeat();
  const jitter = Math.floor(Math.random() * intervalMs);
  setTimeout(() => {
    sendPayload({ op: 1, d: lastSequence });
    heartbeatInterval = setInterval(() => {
      sendPayload({ op: 1, d: lastSequence });
    }, intervalMs);
  }, jitter);
}

function stopHeartbeat() {
  if (heartbeatInterval) {
    clearInterval(heartbeatInterval);
    heartbeatInterval = null;
  }
}

function connect(token: string, logger: Logger, isResume = false) {
  if (destroyed) return;

  const url = isResume && resumeUrl ? resumeUrl : GATEWAY_URL;
  ws = new WebSocket(url);

  ws.onopen = () => {
    if (isResume && sessionId) {
      sendPayload({
        op: 6,
        d: { token, session_id: sessionId, seq: lastSequence },
      });
    } else {
      sendPayload({
        op: 2,
        d: {
          token,
          intents: 0,
          properties: {
            os: "linux",
            browser: "whispergate",
            device: "whispergate",
          },
          presence: {
            status: "online",
            activities: [{ name: "Moderating", type: 3 }],
          },
        },
      });
    }
  };

  ws.onmessage = (evt: MessageEvent) => {
    try {
      const msg = JSON.parse(typeof evt.data === "string" ? evt.data : String(evt.data));
      const { op, t, s, d } = msg;

      if (s) lastSequence = s;

      switch (op) {
        case 10: // Hello
          startHeartbeat(d.heartbeat_interval);
          break;
        case 11: // Heartbeat ACK
          break;
        case 1: // Heartbeat request
          sendPayload({ op: 1, d: lastSequence });
          break;
        case 0: // Dispatch
          if (t === "READY") {
            sessionId = d.session_id;
            resumeUrl = d.resume_gateway_url;
            logger.info("whispergate: moderator bot connected and online");
          }
          if (t === "RESUMED") {
            logger.info("whispergate: moderator bot resumed");
          }
          break;
        case 7: // Reconnect
          logger.info("whispergate: moderator bot reconnect requested");
          ws?.close(4000);
          break;
        case 9: // Invalid Session
          logger.warn(`whispergate: moderator bot invalid session, resumable=${d}`);
          if (d) {
            scheduleReconnect(token, logger, true);
          } else {
            sessionId = null;
            scheduleReconnect(token, logger, false);
          }
          break;
      }
    } catch {
      // ignore
    }
  };

  ws.onclose = (evt: CloseEvent) => {
    stopHeartbeat();
    if (destroyed) return;
    const code = evt.code;
    if (code === 4004) {
      logger.warn("whispergate: moderator bot token invalid, not reconnecting");
      return;
    }
    logger.info(`whispergate: moderator bot disconnected (code=${code}), reconnecting...`);
    const canResume = code !== 4010 && code !== 4011 && code !== 4012 && code !== 4013 && code !== 4014;
    scheduleReconnect(token, logger, canResume && !!sessionId);
  };

  ws.onerror = () => {
    // onclose will fire after this
  };
}

function scheduleReconnect(token: string, logger: Logger, resume: boolean) {
  if (destroyed) return;
  if (reconnectTimer) clearTimeout(reconnectTimer);
  const delay = 2000 + Math.random() * 3000;
  reconnectTimer = setTimeout(() => connect(token, logger, resume), delay);
}

export function startModeratorPresence(token: string, logger: Logger): void {
  destroyed = false;
  connect(token, logger);
}

export function stopModeratorPresence(): void {
  destroyed = true;
  stopHeartbeat();
  if (reconnectTimer) {
    clearTimeout(reconnectTimer);
    reconnectTimer = null;
  }
  if (ws) {
    ws.close(1000);
    ws = null;
  }
}